Earth drilling apparatus

ABSTRACT

A drilling system wherein, even if the drilling direction is not only a downward direction but also any direction, a core can be collected and, even in the case of reaming a part of the bore in the course and also of replacing the bit, the bit can be replaced without recovering the drill stem inserted in the bore.

United States Patent Okuyama et al. Sept. 4, 1973 [54] EARTH DRILLING APPARATUS [51] Int. Cl E2111 9/26 Inventors: Yasushi okuyama, Suginami ku 0 Search Tokyo; Sho Takano, Setagaya-ku,

Tokyo; Ryokuya Suzuki, Niihama, [561 References W ll of Japan UNITED STATES PATENTS Assigneez sumiomo Metal Mining p y gggtock et al 175/258 7 Japan 1,7411497 12 1929 Boltz v. 22 Filed; July 29 1971 3,097,707 7/1963 Kammerer 3,123,160 3/1964 Kammerer 175/260 [21] Appl. No.: 167,441

Related US Application Data Primary Examiner-James A. Leppink [63] Continuation of Ser. No. 41,192, May 28, 1970, Attorney-Watson Cole & Watson 57 ABSTRACT 30 F i li i p i i Data A drilling system wherein, even if the drilling direction June 4 1969 Japan M3204 is not only a downward direction but also any direction, June b I969 Japan 44/4509. 21 core can be collected and, even in the case of reaming June 1969 I3 44/46802 a part of the bore in the course and also of replacing the June .1969 Japan 44/47929 bit, the bit can be replaced without recovering the drill p Stem inserted in the bore- [52] US. Cl. 175/258 2 Claims, 12 Drawing Figures PATENTEDSEP 4 mm 37563531 sum 1 or a A F 2 25 g ulo FIG. 2

ATTORNEY memcnsi 4191s 3.756331 sum 2 or 8 INVENTOR k2,? hi; W55.

PATENTED E 4m 3.756331 SHEEI 3 0F 8 INVENTOR ATTORNEY PATENTED 3i? 4 I975 SHEEI l; 0F 8 FIG.5

BY W PAIENIEDMP 4 ma SHEEI 5 OF 8 INVENT OR fm ATTORNEY PAIENTEDSEP 4 I915 3. 756; 331

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. K I QM 1 Av E 43\\' i: 7 i: 64 I 66- 55 65 \IZ Z INVENT OR ATTORNEY EARTH DRILLING APPARATUS This application is a continuation of Ser. No. 41 l 92, filed May 28, 1970, now abandoned.

This invention relates, to a drilling system In order to investigate or confirm an underground earth quality, a boring operation is normally carried out wherein a cylindrical drill is pushed while being rotated into the ground for taking a core sample.

In this operation, usually an iron pipe or drill stem is connected to the bit and is connected with a driving device the bit, which may have diamond cutters thereon, is rotated about its longitudinal axis to annularly cut a core. At the same time, under pressure water is fed into the drill stem from the ground surface to cool the bit heated during cutting, and the slime produced by the cutting operation is discharged together with water through the outside of the drill stem. In order that the water fed into the ground be discharged onto the ground through the exterior of the drill stem, the bore hole in the ground must be ofa diameter larger than the outside diameter of the drill stem. Therefore, it has been customary for a bit having a cutting part for a hole which is larger than the drill stem, to be connected to the inner end of the drill stem for carrying out the operation. As the core which is cut and taken by the bit enters a core tube connected between the bit and drill stem, the long drill stem inserted deep into the ground must be lifted out in order to extract the core sample. If it is desired to extract the core smaple only without having to recover the drill stem from the hole, it is customary to use a drilling system wherein a core tube is inserted into the bit through the drill stem so that a core which has been cut and taken by the bit may enter this core tube and whereby only the core tube containing the core need be pulled up to the ground surface through the drill stern while leaving the bit and drill stem in place in the ground.

Such a core tube is integrally provided with a latching device to be singly set in the drill stem rid with a lifting device having a connector for pulling it up so that, when the core tube is moved toward the bit through the drill stern by means of running water toward the bit at the tip of the drill stem and is hung with a wire of the lifting device so as to be lowered to a fixed position, the latching device mayfit a recess made inside the drill stem so as to be set and, in the case of pulling it up, the lifting device fastened to the wire may be lowered through the drill stern, may be connected with the connecting device provided in the head part of the core tube, and may thereafter be pulled to the ground surface to disengage the fitting of the latching device and drill stem and to pull up the core tube onto the ground.

Alternatively, an under reamer device has also been used in the past for expanding the hole diameter in any portion of the hole which has been dug by means of the above-mentioned apparatus. Such an under reamer device may be designed as having a blade forming cutting surface of diamond at its inner end projecting from the interior of a tube and having the same outside diameter as of the drill stem. The reamer connected to the lower end or some other desired portion of the drill stem and its blades are projected for reaming the hole during rotation of the drill stem. With such a reamer device, the blades project out of respective windows provided in the tube of the same diameter as of their drill stem nd are supported at the ends by the tube as fulcra in the axial direction of the tube so that. when a conical wedge set in the tube is pushed in the axial direction of the tube by means of hydraulic pressure, the conical surface of the wedge pushes out the blades and the hydraulic pressure releases. The blades may then be partly pulled into the tube by the forces of springs.

Even with the use of such a conventional under reamer device, the entire drill stem must be placed into and taken out of the ground as with other drilling apparatus.

in the above described improved drilling system which makes use of an extractable core tube, it should be noted that the entire drill stem may nevertheless need be pulled out of the ground when the cutting quality of the bit has been reduced, thereby presenting the same disadvantages as with other systems not having core tubes.

An object of the present invention is therefore to provide a drilling system wherein the boring operation may can be carried out more efficiently as compared to other prior art devices, i.e., provision of a drilling system having an under reamer device, the blades of which are brought into contact with the wall of the dulled hole to be reamed, so that, by merely lifting the drill stem as required, the hole can be reamed and, while the drill stem is left inserted in the ground, the bit and core can be taken out.

In order to attain this object, according to the present invention, a latching device is integrally formed on the ground surface side of the under reamer device which can be inserted into a drill stern and in which the blades can ream holes of a diameter larger than the outside diameter of the drill stem, a recess for engaging with this latching device is formed in the end part on the underground side of the drill stem, further parts for defining their relative positions and parts for transmitting rotations are formed in both the drill stem and under reamer device, and a core tube and-core collecting bit fitted directly to the end part on the underground side of this under reamer device are provided.

The present invention also includes a pate-shaped engaging pawl used in a conventional latching device. Therefore, if an inwardly projecting flaw is present on the pipe wall of the drill stem, the pawl often catches on such flaw and cannot be moved toward the bit since as the pawl is so designed as to be always expanded outwardly by means of a spring while it is being inserted into the lower part by sliding it through the drill stem. Further, the engaging pawl in the conventional latching device is only to be engaged with the exterior drill stem or the outer tube of the core tube in order to prevent the core tube from floating up above a fixed position, and is so designed that the rotating force of the drill stem may not be transmitted to the latching device.

Another objectof the present invention is to provide a drilling system having a latching device which can be perfectly retracted into its outer tube so that the latching pawl will not hang onto a projection within the drill stern, can be combined with the drill stem in the rotating direction, can receive the propelling pressure of the drill stem, can be used as connected with a reaming device, core tube and bit and can make a positive latching so as not to be disengaged by the fluctuation of the hydraulic pressure of water fed into the drill stem; and a latching device which can be perfectly retracted into its outer tube so that the latching pawl will not hang onto a projection within the drill stem; can be combined with the drill stern in the rotating direction; can receive the propelling pressure of the drill stem and can be used as connected with a reaming device, core tube and bit.

Further, when a known conventional under reamer is used as it is for the drilling system of the present invention as one of the objects of the present invention, the below mentioned defect may nevertheless be present. That is to say, although the reaming blades which cut and expand a hole diameter are designed to be opened and closed under hydraulic pressure fed from the ground surface side, the hydraulic pressure may nevertheless diminish in the event that the drilling hole reaches an druse or a crack in the ground during the boring. In such case, the reaming blades are contained in the axial direction of the drill stem, the hole diameter reduces and the drill stem, as a result, cannot advance together with the cutting. So that such a defect will not occur, the present invention includes a drilling system wherein, once the reaming blades project outwardly under hydraulic pressure, the reaming blades do not retract in the axial direction of the drill stem under the influence of the hydraulic pressure reduction or the like but, when it is pulled up onto the ground surface side with a lifting dog (lifting device) lowered from the ground surface, the latching member and the drill stem are disengaged with each other and at the same time the blades of the reaming device can be retracted inside the inside diameter of the drill stem.

In the accompanying drawings:

FIGS. 1 and 2 are sectional views of an embodiment of the drilling system ccording to the present invention, each drawing representing a half-section thereof along both sides of line A-A;

FIGS. 3 to 7 show an embodiment of a latching device forming a part of the present drilling system;

FIG. 3 is a vertical sectional view of the latching member as engaged in the latching position of the drill stem;

FIG. 4 is a vertical sectional view showing the latching member as passing through the drill stem;

FIG. 5 is a vertical sectional view showing the movement of the latching member having a pulling up the latching member from the latching position with a lifting dog;

FIG. 6 is a perspective view of four latching pawls as assembled;

FIG. 7 is a perspective view of a window part of the outer tube of the latching member;

FIG. 8 is a perspective view of an annular spring to radially push the latching pawls;

FIG. 9 is a perspective view showing the relation of the outer tube of the latching member and the latching pawl;

FIG. 10 is a vertical sectional view of an embodiment of an under reamer forming a part of the present drilling system; and

FIGS. 11 and 12 are vertical sectional views of embodiments in which the technique of letting the latching pawls in and out by the latching mechanism in FIG. 5 is modified.

In FIGS. 1 and 2, the left side is the direction of the ground surface and the right side is the direction of the under-ground. An annular recess 2 is formed on the inside surface of the end part on the underground side of the drill stem 1 to prevent a latching device from moving to the ground surface side as engaged with latches 3 of the latching device B in the same position as in a known apparatus. The latching device B is provided in the end part on the ground surface side with a lifting dog, an outer tube 5 provided with a coupling projection 4, a supporting bar 6 of the latches 3 movable in the axial direction of the outer tube 5 therein and a safety device 7 for the latches 3. Their mechanisms and operations are known and therefore shall not be explained here.

In accordance with the present invention, a part is provided to permit the reaming blades 13 of an under reamer device to remain in a fixed position projected ahead of the end part on the underground side of the drill stem 1 and the rotation of the drill stem to be transmitted as shown in FIG. 2. In this embodiment, such a part is defined by a spline 9 formed inside an auxiliary tube 8 threaded into. and connected inside the end part on the underground side of the drill stem 1, a flange 10 formed in the end part on the underground side of the spline 9, a spline 11 formed on the exterior of the outer tube 5 of the latching device B and a flange 12 formed in the end part on the ground surface side. Therefore, when the outer tube 5 is advanced from the ground surface side to the underground side so that the splines 9 and 11 are fitted together, the axial position is defined by the flange 10 or 12 and the rotation of the drill stem is transmitted to the outer tube 5 by the splines 9 and 11. In accordance with the present invention, the supporting bar 6 of the latches 3 is connected with an outer tube 14 of an under reamer device C and is integrally combined with the under reamer device C.

A subject matters of the present invention can be said to be that this under reamer device C is connected with the latches 3 of the latching device B. The structure of the under reamer device illustrated in FIG. 2 is exactly the same as any commercially available one so that it will'be only briefly explained.

A hollow tube 16 is inserted through a sealing ring 15 into the outer tube 14. A coiled spring 17 is inserted on the outer periphery between the sealing ring 15 and the stepped part 16A on the ground surface side of the hollow tube 16 so that the hollow tube 16 may be always pushed to the ground surface side by the tensile strength of this spring 17.

The blade 13 has a spherical shape at end part 18 on the underground side and is supported in this end part 18 by a spherical recess 20 disposed within outer tube 14 so as to be capable of moving in and out with this part as a fulcrum. Further, the blade 13 is pushed in from the end part 18 toward the inside of the outer tube 14 by a spring 19 inserted within a hole made toward the center of the blade 13. A conical surface 21 tapering toward the end part is formed on the outer periphery on the underground side of the hollow tube 16 and the inside of the blade 13 is in contact with the conical surface 21 so that the blade 13 may be pushed out or in by the axial movement of the conical surface 21. A stepped part 23 is made inside the hollow tube 16 having this conical surface 21 and a ball 24 is inserted in this stepped part 23 from the ground surface side. Water under pressure, fed from the ground surface passes between the outer tube 5 and the drill stem 1, enters the outer tube 5 through holes 25 made in the outer tube 5, further enters the supporting bar 6 through holes 26 made in the supporting bar 6, enters the hollow tube 16 and pushes the ball 24. As the ball 24 is in contact with the stepped part, the hollow tube 16 compresses the spring 17 in the axial direction and moves to the underground side so that the larger diameter side of the conical surface 21 may come into contact with the inside surfaces of the blades 13 to push and expand the blades 13.

When there is no feed of water under pressure, an operation reverse to this is made and the blades 13 are pulled in by the springs 19. A bypass for pressurized water is made on the periphery of the ball 24 and extends to the inside of the hollow tube 16 so that pressurized water may pass to the underground side through an inner tube 27 fixed to the outer tube 14. In the equipment of the present invention, the blades 13 are formed to be pulled in so as to be able to pass through the drill team 1.

The roation of the drill stem 1 is transmitted to the outer tube 5 through the splines 9'and 11, to the latches 3 from the outer tube 5, to the supporting bar 6 and outer tube 14 from the latches 3 and to the blades 13 from the outer tube 14.

30 is a sealing ring provided so that water may not leak between the outer tube 5 and the supporting bar 6 in the under reamer device part.

With the above-mentioned structure, reaming can be made by setting the under reamer device c as in the drawing in the end part on the underground side of the drill stem 1 while the drill stem 1 is left in the ground as is and, when the reaming is completed, the latching device is disengaged by any known means and only the under reamer device need be recoeved on the ground surface without pulling up the drill stern. Thus the reaming operation can be carried out effeciently.

Further, as shown in FIG. 2, when a core tube 28 and a bit 29 for cutting and taking a core are connected to the outer tube 14 of the under reamer device 6, even if the outside diameter of the bit 29 is smaller than the outside diameter of the drill stem 1, boring can be advanced while reaming the hole to be larger than the drill stem 1 with the blades 13. Therefore, the drill stem 1 can be advanced without any trouble. Further, as the bit 29 together with the under reamer device c and the core cut and taken in the core tube 28 can be pulled up independently of the drill stem 1, the core can be collected and the bit can be replaced considerably more efficiently than before.

It is needless to say that a latching device, under reamer device and design other structure of any other than shown can be adopted within the scope of the subject matter of the present invention, and that a core catching devicecan be used as connected to the outer tube 14 the same as before.

The part relating to the latching device in FIGS. 3 to 9 is an embodiment forming a part of the prsent invention.

As described in the second object of the present invention, a latching device is provided which can be perfectly retracted into its outer tube so that the latching pawl will not hang on some projection within the drill stem, can be combined with the drill stern in the rotating direction, can receive the propelling pressure of the drill stem, can be used as connected with a reaming device, a core tube and a bit, and can make a positive latching so as not to be disengaged by the fluctuation of the hydraulic pressure of water fed into the drill stem.

This embodiment shall be explained with reference to FIGS. 3 to 9. l is a drill stem designed in the shape of a cone tapered toward the end part and having a gradual spiral spline 33 which rotates in the rotating direction of the drill stem 1 formed on the inside surface of its lower end. An annular recess 34 in the form of a ratchet wheel for engaging in the rotating direction of the drill stem 1, is provided on the inside surface of the drill stem 1 slightly above lower end 32. The latching member to be engaged with this drill stem 1 has an outer tube 35 which can be inserted into the drill stem 1, a first inner tube 36 inserted in the outer tube 35 and a second inner tube 37 provided further inside the first inner tube 36. The outer tube 35 and the second inner tube 37 are integrally combined with one another in the end part 38 on the ground surface side and an engaging piece 39 to be coupled with a lifting device (lifting dog) to the ground surface is provided so as to be free to come in and out in the axial direction in the end part 38.

A stepped part 40 is formed inside the end part on the ground surface side of the first inner tube 36 so that the first inner tube may move in the axial direction relative to outer tube 36 by a distance between the stepped part 40 and a flange 41 formed on the outer periphery of the second inner tube 37. A spring 42 stretching in the axial direction is inserted between the end part 38 on the ground surface side and the stepped part 40 of the first inner tube 36. The outer tube 35 is provided with four windows 43 at regular intervals on its peripheral surface and is also provided at its lower end with a spline 44 adapted to fit the spline 33 of the drill stem 1.

The end part on the under-ground side of the second inner tube 37 is designed as having a conical surface 45 tapered on the outside surface toward the underground side. Latching pawls, 46 each having on its inside surface, the same curved surface 48 as conical surface 45 are inserted respectively in the windows 43 of outer tube 35 and windows 47 of the first inner tube. As shown in FIG. 6, latching pawl 46 comprises a partly cut pipe section which is curved on the outer peripheral surface in the same direction as that of curved surface 48, is parallel with the center axis of the curved surface 48, is provided with a cylindrical surface 49 having an eccentric center axis and with a stepped part 50 parallel with the axial direction on the projecting side of the cylindrical surface 49 and has a surface at right angles I with the center axis of the curved surface 48 formed on each of the upper and lower end surfaces 51. FIG. 6 shows four latching pawls 46 as cylindrically assembled. The latching pawls 46 are to be arranged at intervals of a width substantially equal to this peripheral width in the outer tube 35 and first inner tube 36.

The window 47 through which latching pawl 46 projects is of a size as to just embrace latching pawl 46. Further, the axial length of the window 43 of outer tube 35 is made larger than the axial length of the latching pawl 46. The edge 52 on the ground surface side is at right angles with the axial direction of the outer tube 35 but the edge 53 on the underground side slopes toward a rotating direction of the drill stem 1 (FIG. 7).

Each latching pawl 46 is provided in the same position with a peripheral groove 54 on the curved inside surface 48 and is arranged as in FIG. 3 on the outer periphery of the conical surface 48 of the second inner tube 37 by fitting in the groove 54 an annular spring 55, partially cut as shown in FIG. 8 which serves to push the latching pawls 46 in the raidal direction. In FIG. 3, a piston 56 is connected to the part extended into the second inner tube 37 of the engaging piece 39 and a spring 57, which is weaker than the spring 42 stretched in the axial direction, is inserted between the piston 56 and the end part 38. A flange 58 is provided outside the second inner tube 37 of the engaging piece 39 to limit the degree of the entry by the spring 57 into the second inner tube 37. The piston 56 is provided with an annular concave groove 59 on its peripheral surface. Pins 60 are provided through the second inner tube 37 are radially movable inwardly and outwardly on the ground surface side above the conical surface 45. Each pin 60 is arranged as to be always pressed in contact with piston 56 within the second inner tube 37 by means of a spring 61.

In the event that the moved latching member is toward the bit by running water made to flow into the ground through the drill stem, as shown in FIG. 4, the first inner tube 36 is pulled out relative to outer tube 35 until the flange 41 of the second inner tube 37 comes into contact with the stepped part 40 and at the same time the engaging piece 39 is pulled out of the second inner tube 37. When the first inner tube 36 is pulled out relative to outer tube 35, as the first inner tube 36 holds the latching pawls 46 within the windows 47 latching pawls 46 are pulled toward the edges 53, shown in FIG. 9 in the windows 43 in the outer tube 35. As the edge 53 pushes the cylindrical surface 49 inward, about the time when the lower end surface 51 of the latching pawl 46 approaches the intersection of the edge of window 43 53 and the edge in the axial direction, the cylindrical surface 49 is perfectly pulled into the inside from the outer peripheral surface and further, when the lower end surface 51 moves to the underground side from edge 53, cylindrical surface 49 is held in contact with the inner peripheral surface of the outer tube 35. At this time, the pin 60 is in contact with the inside of first inner tube 36 on the ground surface side of the stepped part 40 and remains pushed into the second inner tube 37. Therefore, if the device is put into the drill stem in this state, latching pawls 46 are held within the outer tube 35 and do not come out of the outer tube 35 and therefore, even if there is a small projection within the drill stem, the device does not having on it but can reach the bit.

A typical inner core tube is provided on the underground side of the first inner tube 36. When such tube is moved together with the latching member toward the bit and stops in a predetermined position on the inside surface of the bit, the hydraulic pressure of the water being sent into the ground through the drill stem is added to the end part 38 and pushes down the outer tube 35 and second inner tube 37 to the underground side. While the spline 44 of the outer tube 35 fits the spline 33 of the drill stem 1, the outer gube 35 opposes the windows 43 to the L-shaped recess part of the ratchet wheel-shaped annular recess 34 of the drill stem 1.

A projection 62 is provided on the surface of the first inner tube 36 and is fitted in a vertical groove 63 provided on the inside surface of the outer tube 35. Therefore, the first inner tube 36 and outer tube 35 rotate integrally and the latching pawls 46 held by the first inner tube 36 are also opposed correctly to the L-shaped recess part of the annular recess 34. As the windows 43 of the outer tube 35 and the windows 47 of the first inner tube 36 overlap with one another, by the action of the conical surface 48 of the second inner tube and the spring 55, as in FIG. 9, the cylindrical surface 49 of the latching pawl 46 projects out of the window 43 and its stepped part 50 overlaps on the stepped part of the L-shaped recess part of the annular recess 34. Therefore, the latching member is engaged with the drill stem 1 and inner core tube can be fixed so as not to move toward the ground surface. Further, the rotation of the drill stem 1 is transmitted to the latching pawl 46 corresponding to the pawl of the ratchet from the annular recess 34 corresponding to the ratchet wheel and to the first inner tube 36 from the latching pawl 46. The propelling pressure for the drill stem into the ground is transmitted to the upper end surface 51 of the latching pawl 46 from the stepped part 64 on the ground surface side and the latching pawl 46 transmits it to the first inner tube 36. Therefore, ti is possible to use the bit and reaming device as connected to the lower end of the first inner tube.

After the latching pawl 46 is correctly set in the annular recess 34 of the drill stem 1 and the latching is completed as in the above, the hydraulic pressure acts on the engaging piece 39, the tensile strength of the spring 57 cooperates with it to push the engaging piece 39 into the second inner tube 37, the pin 60 fitted in the concave groove 59 of the piston 56 as in FIG. 4 is pushed out of the concave groove 59 as in FIG. 3 so as to project out of the outer periphery of the second inner tube 37 below the stepped part 40 of the first inner tube 36. With this pin 60, the first inner tube 36 can no longer move relative to outer tube 35 under the force of the spring 42 and therefore the latching by the latching pawl 46 is safely held so as not to be disengaged by the fluctuation of the hydraulic pressure.

Now, in the case of pulling the latching member up to the ground surface by disengaging the latching from the latching position in FIG. 3, if the lifting dog is connected with the engaging piece 39 and is pulled to the ground surface side as known, first of all, the piston 56 compresses the spring 57 and moves toward the end part 38 as shown in FIG. 5 from the state in FIG. 3, the pin 60 is pushed by the spring 61, fits in the concave groove 59 and retracts into the inside from the outer periphery of the second inner tube 37. If the engaging piece 39 is pulled to the ground surface side in the state in FIG. 5, the outer tube 35 is forcibly made to rise with respect to the first inner tube 36 by the tensile strength of the spring 42 and the lifting force, therefore the edge 53 of the window 43 of the outer tube 35 gradually overlaps on the cylindrical surface 49, the latching pawl 46 is pushed into the outer tube 35 against the spring and, as in FIG. 4, the latching pawl 46 is held within the outer tube 35. Therefore, the latching member can be placed in the same state as in the case of inserting it into the ground from the ground surface side and therefore the latching pawl 46 can be pulled up while it never contacts the inside surface of the drill stem.

Even in the case that the latching member is lowered into the drill stem by the gravity without using the lifting dog, the latching can be made with the dropping force in the same manner as in the above mentioned case of setting with the running water pressure. According to the present apparatus, the latching can be positively held with the pins 60. Further, even at the time of inserting and lifting it, by the action of the spring 42 to push to first inner tube 36 to the outside of the outer tube 35 and the frictional force with which the pin 60 is pressed by the spring 61 into contact with the inner surface of the first inner tube 36, the latching pawls 46 are held so as not to project out of the outer tube 35 and therefore there never occurs a trouble that the latching pawl 46 projects out of the outer tube 35 and stops by hanging on the drill stem in the course.

A further objective of the present drilling system is to carry out a more efficient drilling operation by connecting an under reamer to the tip of the latching mechanism and further connecting a bit to the forward end of the under reamer part. However, as already described the already marketed under reamer shown in FIG. 2 may possibly be troublesome in that the diameter of the bore hole made in the ground varies with the fluctuation of the hydraulic pressure. FIG. 10 as an embodiment of an under reamer illustrates a means which avoids this possibility. FIG. 10 is a vertical sectional view showing a reaming device formed as connected with a latching member in a manner as to be able to ream a bore by engaging a reaming member at the lower end of the drill stem.

A gradually twisted spline 68 is provided inside the lower end of the drill stem 1 and a recess 34 for engaging with the latching pawls 46 in the rotating direction and axial direction of the drill stem 1, is provided a short distance above the spline 68.

When the latching member 69 is lowered into the ground through the drill stem by any well known method, its outer tube 35 fits the spline 68 of the drill 'stem 1 with the spline 44 provided on the outer periphery of its lower end and slowly rotates so that the latching pawls 46 held by the latching member 69 may be set in a position opposed to the recess 34 of the drill stem 1 in the peripheral direction.

When the latching member 69 is to be lowered through the drill stem, the first inner tube 36 inserted into the outer tube 35 so as not to rotate relative to the outer tube 35 but capable of moving in the axial direction is relatively pulled out to the underground side (in the direction indicated by X in the drawing) and the latching pawls 46 are retracted into the outer tube 35.

Such an arrangement is formed as follows in this embodiment. The latching pawl 46 consists of a square piece, has the periphery held by a window 47 made through the first inner tube 36, extends outwardly of the outer tube 35 and top part 38 and is disposed in contact with the second inner tube 37 extending into the first inner tube 36. The inside of the latching pawl 46 slopes inwardly and downwardly and the part of the second inner tube 37 in contact with this slope is also made the same slope 45 inclined toward the underground side.

The surface side of the latching pawl 46 is curved along the inside of the outer tube 35 in the peripheral direction of the outer tube 35 and the width in the peripheral direction of the window 43 of the outer tube 35 is of such length as can project the latching pawl 46 so as to fit within recess 34 in the drill stem 1. Also, the axial length of the window 43 is larger than the axial length of latching pawl 46 and the part longer than the latching pawl 46 on the underground side is curved elliptically in the direction indicated by the arrow X. Therefore, if the first inner tube 36 is pulled out in the direction X relative to outer tube 35 and second inner tube 37, latching pawl 46 held by it is moved toward the elliptical edge of the window 43, is pushed into the inside by the edge and moves to the inside along the slope so that the surface side may be inside from the outer peripheral surface of the outer tube 35. The structure wherein the latching pawls 46 are thus made to come in and out by the inner tube provided so as to be able to come into and out of the outer tube 35 may be of a shape other than shown by this embodiment.

Now, when the spline 44 of the latching member 69 lowered into the ground as mentioned above fits within the spline 68, the lower end of the first inner tube 36 contacts a projection 70 provided on the inside surface of the lower end of the drill stem 1 and is pushed into the outer tube 35, therefore the latching pawls 46 are moved to positions in which they are projected out of the windows 43 and are at the same time pushed out to be fitted in the recess 34 in the drum stem 1 by the slopes. A wedge member 83 having a surface 71 sloping downwardly and outwardly is located below the slope 45 of the second inner tube 37. A tube 72 connected to the first inner tube 36 is provided with pins 73 in the direction intersecting at right angles with its axis. A lever 73. pivoted on each of these pins 73 as a fulcrum is pressed at one end against the slope 71. A spring 74 is located about a pin 75 fixed to the first inner tube 36 so as to be able to move up and down in an axial groove 76 made in the second inner tube 37.

To the other end of the lever 73 are fixed columnar bits 77 at one end. Each bit 77 is so provided as to be able to extend outwardly of drill stem 1 below its lower end through tube 72 in the radial direction. On the inside surface of a hole 78 holding the bit 77 provided in the tube 72, is an annular groove 79, and an annular groove is provided on the outer periphery of a bit 77 in which is fitted a ringshaped spring 81 formed so that half its cross-section may be outside the groove 80 in a free state. The depth of the groove 80 is such that this spring 81 may be well embedded in the groove. It is so designed that, in a position in which the end of the bit 77 projects slightly outwardly of the outer periphery fo the drill stem 1, the grooves 79 and 80 may be opposed to each other and a part of the cross-section of the spring 81 may fit in the groove 79. When the first inner tube 36 is out on the underground side with respect to the outer tube 35 (in the case of inserting through the drill stem), as the lever 73' has moved to the underground side together with the first inner tube 36 with respect to the second inner tube 37, one end of the lever 73' contacts thelower side of the slope 71 due to the spring 74 and therefore the outer end of the bit 77 is held as pulled to be inside the part of the smallest inside diameter of th drill stem by disengaging-the spring 81 from the groove 79.

When the latching member 69fits in the recess 34 of the drill stem 1, the first inner tube 36 and the second inner tube 37 become engaged with each other as in the drawing, there-fore one end of the lever 73' contacts the higher side of the slope 71 and the other end of the lever 73' pushes the bit 77 outward with it until the outer end of the bit 77 is pushed out to be a little outside the outer periphery of the drill stem 1. Then the grooves 79 and 80 are opposed to each other and the spring 81 compressed in the groove 80 by the inside surface of the hole 78 fits as partly expanded in the groove 79. By the action of this spring 81, the diameter of the hole reamed with the bits 77 is held so stably as not to be varied by the fluctuation of the feed water pressure.

In the above embodiment, it is possible to provide the slope 71 outside the second inner tube 37. Obviously the type of spring 74 to be used and other elements of this embodiment may be varied without departing from the scope of the invention.

What is claimed is:

1. A drilling system comprising a drill stem and an under reamer means disposed for insertion through said stem, the blades of said reamer means being capable of reaming a hole of a diameter larger than the outside diameter of said drill stem, latching means formed integrally on the ground surface side of said reamer means, members for defining relative positions formed in both said drill stem and said reamer means, a member for transmitting rotation, said drill stem having an annular recess in the form of a ratchet wheel on its inner surface engaging with said latching means and formed in the end part on the underground side of said drill stem, an outer tube capable of being inserted into said drill stern, a second inner tube provided within said outer tube so as to be integral with said outer tube in the end part on the ground surface side, a first inner tube having a stepped part on its inner surface and being disposed between said outer tube and said second inner tube in such a manner as to avoid relative rotation but to permit relative movement in the axial direction, a spring being provided for pushing said first inner tube outwardly of said outer tube, said outer tube being provided with windows, said first inner tube also being provided with windows, said latter window holding a latching pawl with edges in an axial direction and a direction at right angles to said axial direction, the former window having its edge on the ground surface side at right angles with the axial direction and having its edge on the underground side inclined diagonally in the rotating direction of the drill stem, a conical surface of a diameter smaller on the underground side provided on the outer periphery of said second inner tube, a curved surface coinciding with said conical surface formed inside said latching pawl, the outside surface of said latching pawl being parallel with the center axis of said curved surface, an eccentric cylindrical surface and a stepped part parallel with the axial direction on its projecting side being provided, a surface at right angles with the center axis of the curved surface being formed on each of the upper and lower end surfaces, said cylindrical surface being so formed as to project out of said former window, pins being provided as passed in the radial direction along the peripheral surface through said second inner tube, an engaging piece for a lifting dog being provided so as to be able to come into and out of said second inner tube, a piston having an annular concave groove being connected to said second inner tube and said pin being provided so as to be passed against the outer peripheral surface of said piston by a spring and to be able to engage with the stepped part of said first inner tube.

2. A drilling system comprising a drill stem and an under reamer means disposed for insertion through said stem, the blades of said reamer means being capable of reaming a hole of a diameter larger than the outside diameter of said drill stem, latching means formed integrally on the ground surface side of said reamer means, members for defining relative positions formed in both said drill stem and said reamer means, a member for transmitting rotation, said drill stem having a recess on its inner surface and formed in the end part on the underground surface of said drill stem, and the surface parallel to the axial direction of latching pawls defining said latching means, an outer tube capable of being inserted into said drill stem, an inner tube disposed for movement into and out of said outer tube, said outer tube being provided with windows, said inner tube also being provided with windows, each latter window holding a latching pawl with edges in the axial direction and at a directi0n at right angles to said axial direction, said latching pawl being so provided as to be able to radially come into and out of the former window parallel to the direction at right angles with the axial direction by the relative axial movements of said outer tube and inner tube, the upper end surface of said latching pawl being formed as a surface at right angles with the axial direction and at least one surface of the latching pawl opposed to the surface in the axial direction of the former window being formed as parallel to the axial direction. 

1. A drilling system comprising a drill stem and an under reamer means disposed for insertion through said stem, the blades of said reamer means being capable of reaming a hole of a diameter larger than the outside diameter of said drill stem, latching means formed integrally on the ground surface side of said reamer means, members for defining relative positions formed in both said drill stem and said reamer means, a member for transmitting rotation, said drill stem having an annular recess in the form of a ratchet wheel on its inner surface engaging with said latching means and formed in the end part on the underground side of said drill stem, an outer tube capable of being inserted into said drill stem, a second inner tube provided within said outer tube so as to be integral with said outer tube in the end part on the ground surface side, a first inner tube having a stepped part on its inner surface and being disposed between said outer tube and said second inner tube in such a manner as to avoid relative rotation but to permit relative movement in the axial direction, a spring being provided for pushing said first inner tube outwardly of said outer tube, said outer tube being provided with windows, said first inner tube also being provided with windows, said latter window holding a latching pawl with edges in an axial direction and a direction at right angles to said axial direction, the former window having its edge on the ground surface side at right angles with the axial direction and having its edge on the underground side inclined diagonally in the rotating direction of the drill stem, a conical surface of a diameter smaller on the underground side provided on the outer periphery of said second inner tube, a curved surface coinciding with said conical surface formed inside said latching pawl, the outside surface of said latching pawl being parallel with the center axis of said curved surface, an eccentric cylindrical surface and a stepped part parallel with the axial direction on its projecting side being provided, a surface at right angles with the center axis of the curved surface being formed on each of the upper and lower end surfaces, said cylindrical surface being so formed as to project out of said former window, pins being provided as passed in the radial direction along the peripheral surface through said second inner tube, an engaging piece for a lifting dog being provided so as to be able to come into and out of said second inner tube, a piston having an annular concave groove being connected to said second inner tube and said pin being provided so as to be passed against the outer peripheral surface of said piston by a spring and to be able to engage with the stepped part of said first inner tube.
 2. A drilling system comprising a drill stem and an under reamer means disposed for insertion through said stem, the blades of said reamer means being capable of reaming a hole of a diameter larger than the outside diameter of said drill stem, latching means formed integrally on the ground surface side of said reamer means, members for defining relative positions formed in both said drill stem and said reamer means, a member for transmitting rotation, said drill stem having a recess on its inner surface and formed in the end part on the underground surface of said drill stem, and the surface parallel to the axial direction of latching pawls defining said latching means, an outer tube capable of being inserted into said drill stem, an inNer tube disposed for movement into and out of said outer tube, said outer tube being provided with windows, said inner tube also being provided with windows, each latter window holding a latching pawl with edges in the axial direction and at a directi0n at right angles to said axial direction, said latching pawl being so provided as to be able to radially come into and out of the former window parallel to the direction at right angles with the axial direction by the relative axial movements of said outer tube and inner tube, the upper end surface of said latching pawl being formed as a surface at right angles with the axial direction and at least one surface of the latching pawl opposed to the surface in the axial direction of the former window being formed as parallel to the axial direction. 